Thursday, July 16, 2015

Crop response to different tillage systems and crop rotations is highly influenced by soil conditions that include soil drainage class; soil texture; soil organic matter; water holding capacity; and weather variables, such as temperature, precipitation amount and distribution, and frost-free days. In a study conducted by Iowa State University, corn yield and economic return with different tillage systems and crop rotations were highly influenced by regional soil and climate conditions. The study was conducted at seven locations in Iowa from 2003 to 2013. The experiment involved five tillage systems (no-tillage, NT; strip-tillage, ST; chisel plow, CP; deep rip, DR; and moldboard plow, MP).Three crop rotations of corn–soybean, C–S; corn–corn–soybean, C–C–S; and corn–corn, C–C were evaluated. The objectives were to: (i) investigate seasonal variability in corn yield as affected by tillage and crop rotation, (ii) identify appropriate tillage for each crop rotation and location, and (iii) evaluate the magnitude of crop rotation effect on corn yield.

Corn yields varied from 40 to 252 bu/A with no detectable increase over time. The input cost for corn production was greater with conventional tillage systems over NT and ST by 7.5 and 5.7%, respectively. Yield and economic returns for the three rotations were as follow: C–S > C–C–S > C–C. Yield and economic penalty were greater with NT than conventional tillage in the northern locations (poorly-drained soils) than locations with well-drained soils. The corn yield penalty associated with C–C was location specific and varied from 11 to 28%. The findings suggest a location specific adoption of tillage and crop rotation for achieving optimum yield.

Implications
The corn yield response to different tillage systems within each crop rotation was similar with a
few exceptions. The adoption of NT or ST practices in combination with a C–S rotation has lower risk for yield and economic return losses as compared to C-C-S or C-C rotation.The results of this study suggest that at locations with well-drained soils, NT and ST can be competitive in terms of yield and economic return as compared to conventional tillage systems.

Wednesday, July 8, 2015

Often growers ask the question, "What if I had done one more thing to this year's crop - would it have affected yield? In a study conducted by researchers at the University of Illinois during 2009 and 2010, five management factors were assessed for their individual and cumulative contributions to corn yield and yield components in a corn-soybean rotation. Five management factors involving plant population, transgenic insect resistance, fungicide containing strobilurin, P–S–Zn fertility, and N fertility were evaluated. A standard treatment was used that simulated commercial corn production. This standard treatment was compared to other treatments involving each additional input and a high technology treatment where all supplemental treatments were applied.

The high technology treatment yielded 46 bu/A (34 to 56 bu/A) more grain (28%) than the standard treatment, This demonstrates a yield gap between traditional commercial farm practices and the attainable yield using available technologies. All management factors except plant population were necessary for reducing the yield gap. Fungicide and transgenic insect resistance traits provided the greatest yield increases. Averaged over sites and years, if each factor was withheld from the high technology system, yield decreased by decreasing kernel number. Increased plant population reduced the yield gap when all other inputs were applied at the supplemental level. Kernel number was more significant for increasing yield than kernel weight. Thee yield contribution of each technology was greater when applied as part of a full complement of supplemental inputs than when added individually to the standard commercial system.

Implications
Although economics are not considered in this article (only yield response), the fact that a 28% yield gain could be obtained with available technology is intriguing. The other important conclusion by the authors is that the technologies are synergistic - all must be used to realize this gain. Yet, the experimental design (omission plots) is NOT able to identify specific interactions between a subset of the management factors. So this conclusion needs further study. It may be that two or three of the factors provide the major yield increase.